The miniaturization of semiconductor circuit elements has reached a point where feature sizes of 45 nm, 32 nm, 28 nm and even 20 nm are fabricated on a commercial scale. As the dimensions continue to get smaller, new challenges arise for process steps like filling a gap between circuit elements with a variety of materials. As the width between the elements continues to shrink, the gap between them often gets taller and narrower, making the gap difficult to fill without the dielectric material getting stuck to create voids and weak seams. Conventional chemical vapor deposition (CVD) techniques often experience an overgrowth of material at the top of the gap before it has been completely filled. This can create a void or seam in the gap where the depositing dielectric material has been prematurely cut off by the overgrowth; a problem sometimes referred to as breadloafing.
One solution to the breadloafing problem has been to use a silicon precursor and a plasma-excited precursor combined in a plasma-free substrate processing region to form a nascently-flowable dielectric film. The as-deposited flowability allows the film to fill gaps with a silazane-containing film using this chemical vapor deposition technique. The silazane film may be processed subsequently to transition the film to, for example, silicon oxide. Such a chemical vapor deposition has been found to produce better gapfill properties than spin-on glass (SOG) and spin-on dielectric (SOD). While the deposition of flowable dielectric films deposited by CVD has fewer breadloafing problems, such techniques are still unavailable for some classes of material.
While the new flowable CVD techniques represent a significant breakthrough in filling tall, narrow (i.e., high-aspect ratio) gaps with dielectric materials such as silicon-containing films such as silicon-nitride-hydride and silicon oxide, there is still a need for techniques that can seamlessly fill such gaps with carbon materials. Among other topics, the present application addresses this need by describing flowable CVD techniques for forming carbon films on a substrate.